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<h2><a name="SECTION008360000000000000000"></a><a name="decimal-threads"></a>
<br>
6.3.6 Working with threads 
</h2>

<p>
The <tt class="function">getcontext()</tt> function accesses a different <tt class="class">Context</tt>
object for each thread.  Having separate thread contexts means that threads
may make changes (such as <code>getcontext.prec=10</code>) without interfering with
other threads.

<p>
Likewise, the <tt class="function">setcontext()</tt> function automatically assigns its target
to the current thread.

<p>
If <tt class="function">setcontext()</tt> has not been called before <tt class="function">getcontext()</tt>,
then <tt class="function">getcontext()</tt> will automatically create a new context for use
in the current thread.

<p>
The new context is copied from a prototype context called
<var>DefaultContext</var>. To control the defaults so that each thread will use the
same values throughout the application, directly modify the
<var>DefaultContext</var> object. This should be done <em>before</em> any threads are
started so that there won't be a race condition between threads calling
<tt class="function">getcontext()</tt>. For example:

<p>
<div class="verbatim"><pre>
# Set applicationwide defaults for all threads about to be launched
DefaultContext.prec = 12
DefaultContext.rounding = ROUND_DOWN
DefaultContext.traps = ExtendedContext.traps.copy()
DefaultContext.traps[InvalidOperation] = 1
setcontext(DefaultContext)

# Afterwards, the threads can be started
t1.start()
t2.start()
t3.start()
 . . .
</pre></div>

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